(a) Field of the invention
The present invention relates generally to an integrated semiconductor device, and especially it pertains to an integrated semiconductor device of the IIL type wherein a static induction transistor is used as the switching transistor.
(b) Description of the prior art
Among known integrated semiconductor devices of the IIL (Integrated Injection Logic) type, SITL (Static Induction Transistor Logic) devices are a unique and attractive version wherein a static induction transistor (hereinafter to be abbreviated as SIT) of a normally-off mode is used for the driver or switching transistor. The SITL device features excellent operation characteristic, straghtforward simple manufacturing process and high inregration density, which is due mainly to the use of the SIT.
The SIT of a normally-off mode employed in the known SITL device is formed with current channels sorrounded by a gate which constitutes pn junctions with the channels. When no gate bias voltage is applied, the channels are substantially pinched off by depletion layers extending from the gate, and therefore the SIT is in the non-conducting state. With a forward gate bias voltage applied to the gate, however, the depletion layers are caused to shrink to turn the channels conductive. In general, the operation speed and the capability of funouts of the entire SITL device are essentially limited by and subject to the operation performance of the SIT employed. Namely, the operation characteristics of the SITL device can be improved by employing an improved SIT that can provide a higher current gain which is the drain current divided by the gate current, a higher transconductance and a higher switching speed.